1. Field of the Invention:
The present invention is directed to a circuit for protecting a high voltage integrated circuit for driving power transistors in a half bridge configuration, allowing for excessive negative swing of the output node.
2. Description of the Related Art:
In driver circuits for power transistors, for example, power MOSFETs driving power equipment, the power transistors often switch a large current. The large switching current, combined with forward recovery characteristics of diodes and stray inductance in the circuit, generates a negative spike at the output node of the half bridge. These spike signals can be destructive to the driver circuits and also create noise.
It is accordingly, an object of the present invention to provide a circuit for driving power transistors in a half bridge configuration allowing for excessive negative swing of the output node.
It is furthermore an object of the present invention to provide such a circuit which can be integrated on a single chip.
The above and other objects of the invention are achieved by providing a resistor between the substrate of the high voltage integrated circuit chip (HVIC) and ground potential (i.e., the common potential terminal (COM)) of the chip.
It has been found that including a resistor between the substrate and ground of the HVIC substantially improves the handling of negative voltage spikes by limiting the current passing through the intrinsic diode of the chip when the diode conducts due to negative transients at the output node.